From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 09DDCC433EF for ; Tue, 22 Feb 2022 07:04:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230365AbiBVHEe (ORCPT ); Tue, 22 Feb 2022 02:04:34 -0500 Received: from gmail-smtp-in.l.google.com ([23.128.96.19]:48738 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230338AbiBVHEd (ORCPT ); Tue, 22 Feb 2022 02:04:33 -0500 Received: from mail-pl1-x62b.google.com (mail-pl1-x62b.google.com [IPv6:2607:f8b0:4864:20::62b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4DB7E113D82; Mon, 21 Feb 2022 23:04:08 -0800 (PST) Received: by mail-pl1-x62b.google.com with SMTP id 4so6193613pll.6; Mon, 21 Feb 2022 23:04:08 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=WkP07DKCbnwQE6/X/KtSc8NN0wE1LkkRJITLBD5bT90=; b=Cgx51X5dhq03DBMkBAJBWHdLdLyireOnBdbzOl2oT9vlfuAYIlhMTYKGJHSlvW27S6 0HY1tzvVTiMBESKMcAsNU6tMe3HF2nyIHG7nz50LXCFS7/Soze9Owm3gbrpw1vmIXpk9 aDk7l8TOBo1nce1rOcqr6lfPpNbBOU+TgwuTBAw++Ji9RQtfrZ3wqqG0FIjtCKNcmnlN hottNQ1a656FeUT20hFC2aMfgpkpyneRxDxc+Qs8asDpksx7yMroDw7kcBPswtIhPQH7 7oheje+5enoeG+9d/nEdlW76mAVFgL46Y21tLYplKbUbeXda8lFZIHZbOxV+szjkiwn2 u5jA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=WkP07DKCbnwQE6/X/KtSc8NN0wE1LkkRJITLBD5bT90=; b=pMwUnCKv4R13RLZ8Zt7NFIGaXg8ZyA9MColXnCphwUbrnlboozIixr4kLuMYNngcCB t8nTnZ05v/cpVKqrPv3vsnOA06AxoIITVMPNA+axAsEQaYYDZZAt3zxE+aromssi3J2u fiWP/vqjiKnwbtqu+rWX42SUryHbH8dC14qPBRCtYbyiVmfgfjj2zG8k8AvsBn0Byoid TWA8K318lLbLIekoy5cPYgrpAobPvxXbxkEhUueeFlwef3/FPSBm6hcmvPmTXSw2WrwD WfVn1JkG7CZE8zr81G6qcElXie98ezvvJwZ/4zd/b26j0CChaFyvn9Tzq3M9KB3w5N49 lFDg== X-Gm-Message-State: AOAM531WFAtuRoXhwTUuV9dL25lhCvFFPrQNJ8NZ/OxBYKwK4H0RcO51 rt1wUHrc/6QFhPr3WO+eOBI= X-Google-Smtp-Source: ABdhPJwEetUDw7xT6SNpQSeqBZeZ+X0VRGWtjPz6uapq4dZPXheAHZAioRRI5YVe6Eo5i+1//9ZncQ== X-Received: by 2002:a17:90b:3b46:b0:1bc:4bc4:2f64 with SMTP id ot6-20020a17090b3b4600b001bc4bc42f64mr2700450pjb.203.1645513447686; Mon, 21 Feb 2022 23:04:07 -0800 (PST) Received: from ast-mbp.dhcp.thefacebook.com ([2620:10d:c090:400::5:e2d6]) by smtp.gmail.com with ESMTPSA id i17sm19190986pgn.82.2022.02.21.23.04.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Feb 2022 23:04:07 -0800 (PST) Date: Mon, 21 Feb 2022 23:04:05 -0800 From: Alexei Starovoitov To: Kumar Kartikeya Dwivedi Cc: bpf@vger.kernel.org, Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= , Jesper Dangaard Brouer , netfilter-devel@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH bpf-next v1 08/15] bpf: Adapt copy_map_value for multiple offset case Message-ID: <20220222070405.i6esgcf7ouqrmoef@ast-mbp.dhcp.thefacebook.com> References: <20220220134813.3411982-1-memxor@gmail.com> <20220220134813.3411982-9-memxor@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220220134813.3411982-9-memxor@gmail.com> Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Sun, Feb 20, 2022 at 07:18:06PM +0530, Kumar Kartikeya Dwivedi wrote: > The changes in this patch deserve closer look, so it has been split into > its own independent patch. While earlier we just had to skip two objects > at most while copying in and out of map, now we have potentially many > objects (at most 8 + 2 = 10, due to the BPF_MAP_VALUE_OFF_MAX limit). > > Hence, divide the copy_map_value function into an inlined fast path and > function call to slowpath. The slowpath handles the case of > 3 offsets, > while we handle the most common cases (0, 1, 2, or 3 offsets) in the > inline function itself. > > In copy_map_value_slow, we use 11 offsets, just to make the for loop > that copies the value free of edge cases for the last offset, by using > map->value_size as final offset to subtract remaining area to copy from. > > Signed-off-by: Kumar Kartikeya Dwivedi > --- > include/linux/bpf.h | 43 +++++++++++++++++++++++++++++++--- > kernel/bpf/syscall.c | 55 ++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 95 insertions(+), 3 deletions(-) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index ae599aaf8d4c..5d845ca02eba 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -253,12 +253,22 @@ static inline void check_and_init_map_value(struct bpf_map *map, void *dst) > memset(dst + map->spin_lock_off, 0, sizeof(struct bpf_spin_lock)); > if (unlikely(map_value_has_timer(map))) > memset(dst + map->timer_off, 0, sizeof(struct bpf_timer)); > + if (unlikely(map_value_has_ptr_to_btf_id(map))) { > + struct bpf_map_value_off *tab = map->ptr_off_tab; > + int i; > + > + for (i = 0; i < tab->nr_off; i++) > + *(u64 *)(dst + tab->off[i].offset) = 0; > + } > } > > +void copy_map_value_slow(struct bpf_map *map, void *dst, void *src, u32 s_off, > + u32 s_sz, u32 t_off, u32 t_sz); > + > /* copy everything but bpf_spin_lock and bpf_timer. There could be one of each. */ > static inline void copy_map_value(struct bpf_map *map, void *dst, void *src) > { > - u32 s_off = 0, s_sz = 0, t_off = 0, t_sz = 0; > + u32 s_off = 0, s_sz = 0, t_off = 0, t_sz = 0, p_off = 0, p_sz = 0; > > if (unlikely(map_value_has_spin_lock(map))) { > s_off = map->spin_lock_off; > @@ -268,13 +278,40 @@ static inline void copy_map_value(struct bpf_map *map, void *dst, void *src) > t_off = map->timer_off; > t_sz = sizeof(struct bpf_timer); > } > + /* Multiple offset case is slow, offload to function */ > + if (unlikely(map_value_has_ptr_to_btf_id(map))) { > + struct bpf_map_value_off *tab = map->ptr_off_tab; > + > + /* Inline the likely common case */ > + if (likely(tab->nr_off == 1)) { > + p_off = tab->off[0].offset; > + p_sz = sizeof(u64); > + } else { > + copy_map_value_slow(map, dst, src, s_off, s_sz, t_off, t_sz); > + return; > + } > + } > + > + if (unlikely(s_sz || t_sz || p_sz)) { > + /* The order is p_off, t_off, s_off, use insertion sort */ > > - if (unlikely(s_sz || t_sz)) { > + if (t_off < p_off || !t_sz) { > + swap(t_off, p_off); > + swap(t_sz, p_sz); > + } > if (s_off < t_off || !s_sz) { > swap(s_off, t_off); > swap(s_sz, t_sz); > + if (t_off < p_off || !t_sz) { > + swap(t_off, p_off); > + swap(t_sz, p_sz); > + } > } > - memcpy(dst, src, t_off); > + > + memcpy(dst, src, p_off); > + memcpy(dst + p_off + p_sz, > + src + p_off + p_sz, > + t_off - p_off - p_sz); > memcpy(dst + t_off + t_sz, > src + t_off + t_sz, > s_off - t_off - t_sz); > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index beb96866f34d..83d71d6912f5 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -30,6 +30,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -230,6 +231,60 @@ static int bpf_map_update_value(struct bpf_map *map, struct fd f, void *key, > return err; > } > > +static int copy_map_value_cmp(const void *_a, const void *_b) > +{ > + const u32 a = *(const u32 *)_a; > + const u32 b = *(const u32 *)_b; > + > + /* We only need to sort based on offset */ > + if (a < b) > + return -1; > + else if (a > b) > + return 1; > + return 0; > +} > + > +void copy_map_value_slow(struct bpf_map *map, void *dst, void *src, u32 s_off, > + u32 s_sz, u32 t_off, u32 t_sz) > +{ > + struct bpf_map_value_off *tab = map->ptr_off_tab; /* already set to non-NULL */ > + /* 3 = 2 for bpf_timer, bpf_spin_lock, 1 for map->value_size sentinel */ > + struct { > + u32 off; > + u32 sz; > + } off_arr[BPF_MAP_VALUE_OFF_MAX + 3]; > + int i, cnt = 0; > + > + /* Reconsider stack usage when bumping BPF_MAP_VALUE_OFF_MAX */ > + BUILD_BUG_ON(sizeof(off_arr) != 88); > + > + for (i = 0; i < tab->nr_off; i++) { > + off_arr[cnt].off = tab->off[i].offset; > + off_arr[cnt++].sz = sizeof(u64); > + } > + if (s_sz) { > + off_arr[cnt].off = s_off; > + off_arr[cnt++].sz = s_sz; > + } > + if (t_sz) { > + off_arr[cnt].off = t_off; > + off_arr[cnt++].sz = t_sz; > + } > + off_arr[cnt].off = map->value_size; > + > + sort(off_arr, cnt, sizeof(off_arr[0]), copy_map_value_cmp, NULL); Ouch. sort every time we need to copy map value? sort it once please. 88 bytes in a map are worth it. Especially since "slow" version will trigger with just 2 kptrs. (if I understand this correctly).